Fluorescence probe techniques (FPT) for measuring the relative efficiencies of free-radical photoinitiators

A new method for determining the relative efficiencies of free-radical photoinitiators is reported. Called the fluorescence probe technique (FPT), the method has been used to determine the relative initiation efficiencies of several commercial photoinitiators and new phenyl glyoxylate derivatives in the photopolymerization of a model monomer, triethylene glycol diacrylate. The reactivity of each initiator was measured in reference to that of a standard commercial initiator, 2,2-dimethoxy-2-phenylacetophenone, Irgacure 651. Efficiencies differ widely among the acetophenone derivatives studied, and the phenylglyoxylate initiators are somewhat less reactive than the standard.